Safe-Guard and Panacur have always been around and have always been the same ingredient. Safe-Guard just decided to make their own "power pac" to level the competition
. And, the regular dose fendbendazole dewormers are finally not selling well anymore with education as to its lack of efficacy.
That's great you got something to work. Every situation is difference, so I'm not opposed to using the power-pac, but only as a last resort as you did with your horse. Ivermectin is beginning to show parasite resistence in some areas, so it's important not to over-use it. I only use it twice a year myself.